In a drive plate used in a starter for starting an engine of an automobile, teeth are formed on a peripheral wall disposed in the outer peripheral portion of a disc-like base plate. FIG. 15 is a section view diagrammatically showing a prior art drive plate. As shown in the figure, in the prior art drive plate, a cylindrical portion 2 which is formed by drawing so that it is substantially equal in thickness to a base plate 1 is integrated with the outer peripheral portion of the base plate 1, a cylindrical peripheral wall member 4 wherein teeth 3 are cut in the outer periphery is fitted into the cylindrical portion 2. The peripheral wall member 4 is joined to the cylindrical portion 2 by welding 5.
Even when the peripheral wall member 4 itself has a strength and thickness sufficient for cutting the teeth 3, however, such a drive plate has problems such as defects due to welding failures which are easily produced, requiring an expensive automatic welding robot.
It is an object of the present invention to provide a sheet metal member and a method of thickening an annular peripheral wall of the sheet metal member in which, in a member wherein an annular peripheral wall is formed on a base plate as seen in a drive plate, the base plate and the annular peripheral wall are integrated with each other and teeth can be directly cut in the annular peripheral wall without causing the member to have insufficient strength.